The physics of non-premixed flames is by now well understood. In fact, the structure of such flames has been analyzed mathematically in its entirety in a masterly article by Liñán (1974), which concluded the theoretical work that was initiated by the seminal work of Burke and Schumann (1928). This line of work has established that, for large activation energies (i.e. for all practical flames), the location of the flame as well as several of its properties (e.g. maximum temperature, fuel mass flow rate etc.) are basically determined by mixing. The reactants diffuse into each other and the non-premixed flame establishes itself pretty much like a sheet at the location where the two reactants mix at stoichiometric proportion. This introduces a coupling between the mechanical and chemical characteristics of the flame and its morphology that complicates flame management in practical burners. It is e.g. a matter of everyday experience that by increasing the fuel flow rate of a jet flame we also affect its height, or that there are limitations as to how close to solid surfaces non-premixed flames can sit because of the need for mixing to work.
The early realization that flames contain ions (Lewis (1931), Calcote (1957)) introduced the intriguing possibility of electric control of flames. If one can act on the dilute plasma that the flame generates with appropriately tailored electric fields, it is conceivable that one could affect flame morphology (in a manner that would e.g. be favorable for the purposes of heat transfer) in a way that would be independent of the mechanical and chemical characteristics of the reactive flow. It is by now well-established (Goodings et al. 1979 I & II), that although flames are not hot enough to generate thermal plasmas, some of the combustion intermediates are charged. Exactly because of their chemical nature, these ions are called chemi-ions. Their precise nature has been discoursed intensely in the literature, but the mechanism described in detail in the recent paper by Belhi et al. (2010) that involves the formation of HCO+ and H3O+ seems to be gaining acceptance.
A first line of work in the context of electrostatic manipulation of combustion was the one that related to the combustion of electrostatically charged sprays and solid-particle suspensions. The idea was proposed by Thong and Weinberg (1971) and was followed up by several researchers (Ueda et al., 2002, Okai et al. 2004, Yamamshita and Imamura 2008, Anderson et al. 2008), among which A. Gomez and his collaborators at Yale have provided the most long-lasting and impactful line of work on electrospray combustion (Tang and Gomez (1994), Kyritsis et al. (2004), Lenguito et al. (2014)). Then, there has been substantial work on plasma-assisted combustion (Papac and Dunn-Rankin (2007), Ju and Sun (2015)) although it is realized that introduction and effective control of plasmas requires a very specific set of technologies and that the results, especially as it relates to soot generation, are not always favorable.
Notably, technologies that would involve acting directly on the chemi-ions, without the need for a charged liquid fuel or the generation of the plasma have received very little attention. However, recent analyses have provided data that suggest that this might be possible. In a series of elegant experiments, S. H. Chung and his collaborators showed that electrostatics can affect jet-flame stabilization in a pretty substantial manner (Kim et al. 2012). Laminar flame stabilization was also studied numerically by Belhi et al. (2010), who provided a chemical mechanism for the generation of chemi-ions that was adapted to DNS of laminar flames. The proposed model was somewhat simplified compared to the detailed chemistry proposed in the early work of Goodings et al. (1979 I & II), who established chemi-ions as the main mechanism of charge generation.